Deluge of sewage left in storm's wake

Thousands of gallons of waste in area lakes, streams

Published 10:00 pm, Thursday, December 6, 2007

The deluge that submerged Western Washington early this week also pushed hundreds of thousands of gallons of raw sewage into Seattle-area lakes, streams and homes.

Three days after the heaviest rains abated, King County public utilities managers were still trying to determine how much sewage was released.

But early reports to the Department of Ecology suggest that, at a minimum, 350,000 to 600,000 gallons of untreated sewage flowed into Lake Washington during the storm. Discharges at Green Lake and other areas prompted health authorities to close some beaches.

In Edmonds, some 1,000 gallons of untreated sewage bubbled from a manhole and flowed through a house, leaving a trail of solid waste on the Brookmeyer Drive home's lower level. That stinking stream, like dozens of others, eventually made its way to Puget Sound.

City workers are still trying to estimate how much untreated human waste from a sanitary sewer was diverted into Green Lake after a pump was overwhelmed, said Jason Sharpley, an engineer and adviser at Seattle Public Utilities. Overflows into Lake Washington were also reported in the Windermere neighborhood and at two sites near Seward Park.

Sharpley said the heavy rains also overloaded the city's combined sewer system, which carries both stormwater and sewage.

"It was a real extreme event," Sharpley said. "So far, all our guys can classify it as a greater-than-100-year storm."

Human waste bubbled through several manholes at Myrtle Edwards Park on the Seattle waterfront, prompting King County authorities to cordon off the area. Similar spills occurred in Shoreline's Hidden Lake neighborhood, where several beaches were closed after a pump station moving runoff and sewage was overwhelmed.

Annie Kolb-Nelson, spokeswoman for King County's wastewater-treatment division, said the county treatment plants in Magnolia and Renton were both operating well beyond the norm. At one point during the storm, the Magnolia plant was processing wastewater at a rate of 475 million gallons per day -- about 35 million gallons per day faster than its design maximum.

Kolb-Nelson said sewer operators around the county were forced to divert runoff and sewage into waterways to stop it from backing up into people's homes.

"Our biggest concern is really keeping wastewater away from people," Kolb-Nelson said. "In these extreme emergencies, we'd rather have the sewage flow into a water body than into people's homes and businesses."

Preliminary reports show that untreated human waste was released from county-operated sewers at nine locations, Kolb-Nelson said.

In addition to the sanitary sewer overflows, the county and the city of Seattle also released runoff mixed with a small amount of sewage at dozens of other locations as part of an emergency overflow system.

One of the most severe releases occurred at Medina, where 250,000 to 500,000 gallons of raw sewage flowed into Lake Washington, said Larry Altose, a Department of Ecology spokesman.

Altose said the waste was heavily diluted by rainwater that had found its way into the sanitary sewer. Still, he said, the Ecology Department is urging residents of flood-affected areas to stay out of the water until hard-hit lakes are deemed clean.

King County and the city of Seattle both have plans under way to improve their systems. But Altose said it's difficult to build enough capacity to keep up with the severest storms.

"In the majority of these cases, if not all, the public works community rose to the occasion and did what they could," Altose said. "They had to choose between the lesser of the evils they were facing."